Wet spinning apparatus



nited States wEr SPINNING APPARATUS Victor Emanuel Gonsalves, Arnhem,Netherlands, as-

signor to American Enka Corporation, Enka, N. 6., a corporation ofDelaware This invention relates to an improved method and apparatus forthe jet spinning of viscose rayon.

More particularly, the invention relates to a novel method and apparatusfor the manufacture of artificial threads, fibers and similar productsby a procedure wherein a bundle of viscose jets or filaments emergingfrom a spinneret having a multiplicity of holes in the bottom, iscoagulated and at least partially decomposed by means of suitablecoagulation liquids, such as acid-containing salt baths.

Present day practice in the rayon industry involves for the manufactureof threads, fibers and similar products, a primary drawing-E speed (i.e. the speed at which the freshly formed thread is drawn off from thespinneret) of 6080 meters per minute. Only after stretching is itpossible to increase the speed of travel of the thread.

The method according to the present invention is characterized in thatthe thread, formed by a multiplicity of filaments, is spun from aspinneret freely suspended with the spinning holes downward. Anadjustable amount of coagulation liquid is fed in concentric relationand parallel to the direction of flow of viscose to the face of thespinneret, whereby the coagulation liquid envelopes the multi-filarnentthread like a sheath, and in this form is carried downwardly by thethread, whereupon the resulting thread is aftertreated or wound, orboth, in any well known way.

The coagulation liquid is supplied to the face of the spinneret by meansof a jacket surrounding the viscose supply cylinder or tube to which thespinneret is attached so that the flow of coagulant is parallel to thedirection of flow of the viscose, and whereby the coagulation liquid isdirected near the spinneretface towards the spinning holes. In this waythe coagulation liquid is uniformly spread over the surface of thefreely suspended spinneret holder, and in this way may be fed to thespinneret face.

As a further improvement of the method according to the invention, thethread is advanced on leaving the spinneret by means of a suitablydriven drawing-off roller, and is subsequently stretched.

The apparatus according to the invention, comprising generally a viscosesupply cylinder, a spinneret holder with a spinneret provided with many,e. g., several dozen, spinning holes, and a supply device for thecoagulation liquid, is characterized in that the viscose supply cylinderis placed vertically, or almost vertically, the spinneret holder isconnected with the lower end of the viscose supply cylinder while it isfreely suspended, the spinneret is placed with the spinning holesdownward, and in that the supply device for the coagulation liquid is soconstructed that, during spinning, the coagulation liquid envelopes thethread, consisting of many filaments, like a sheath.

The supply device for the coagulation liquid is preferably soconstructed as to provide concentric access of the coagulation liquid atall sides of the spinneret bottom.

A particularly desirable embodiment of the apparatus according to thepresent invention is characterized in atent "ice that it consists of avessel for pressurizing the coagulation liquid provided with a supplypipe, which vessel is narrowed at the lower end, and of a verticalsupply cylinder for the viscose, going through the vessel justmentioned, which device is connected liquid-tight with the upper end ofthe vessel for the coagulation liquid, whereby the narrowing at thelower end of the vessel for the coagulation liquid surrounds the supplycylinder for the viscose with an annular gap in such a way that thecoagulation liquid can flow to the spinneret bottom over thethus-provided guiding surface. For the proper adjustment of the viscosesupply cylinder or the spinneret holder in the aforesaid annular gap, itis preferred that suitable centering members be included in theapparatus.

In order to prevent turbulence in the flow of the coagulation liquid, itis preferred that the surface constituted by the viscose supply cylinderand/or the spinneret holder for guiding the coagulation liquid be smoothand cylindricalbefore, in and after the aforesaid annular gap. This isbrought about by a smooth transition of the spinneret holder into theviscose supply cylinder on which the holder may be screwed, or by theemployment of a hat-shaped spinneret of which the cylindrical part is ofsuch a length that the connecting parts communicating with the viscosesupply cylinder in the inside of the coagulation liquid vessel are abovethe annular gap.

For a satisfactory flow of the coagulation liquid it is furtherdesirable that the outer diameter of the cylindrical spinneret holder begreater than the spinneret face diameter, and that at the place of thespinneret face there be a smooth bridging over or transition of thisdifference in diameters.

Preferably the edge of the narrowing at the lower side of thecoagulation liquid vessel is formed conically in such a way as to give asharp inward edge. This promotes the easy release of the liquid onleaving the supply device.

It is therefore an object of this invention to provide a method andapparatus that will make it possible to draw off freshly formed threadsof viscose rayon from the spinneret at very high speeds, e. g. overm./min. and even several hundred m./min. Obviously, important advantagesare obtained in this way such as a much greater production than washitherto possible can be achieved with the same number of spinnerets.

Other objects and advantage of this invention will become apparent whenconsidered in conjunction with the accompanying drawings, wherein:

Figure 1 shows a detailed embodiment of the invention in verticalsection;

Figure 2 is a modified form also in vertical section; and

Figure 3 shows schematically the path of the thread in the spinningdevice according to the present invention, from the spinneret to awinding device.

In Figures 1 and 2, 1 denotes a viscose supply cylinder provided at thelower end with a spinneret holder 2 and a flat spinneret 3 provided witha number of spinning holes.

In Figure 1 the spinneret holder 2 is conically narrowed or reduced incross-section in the direction of viscose flow, whereas in Figure 2 thecross-section is uniform.

In Figure 1 the supply cylinder or tube 1 for the viscose is providedwith a conically narrowed spinneret holder 2. Here, the outer surface ofthe holder 2 serves for guiding the coagulation liquid. Surrounding thetube 1 is a jacket 8 for this coagulation liquid. At the upper end,jacket 8 is closed with a stopper 9 provided with a hole for the tube 1.The lower end of the jacket 8 is a cone 10, which may be afiixed to thetube by means of a screw thread. Between the lower end of the cone 10and the tube 1 there is an annular gap 11, through which the coagulationliquid flows uniformly around the outer surface of the spinneret holder2 down to the spinneret 3.

The viscose supply cylinder 1 may be so adjusted by means of set screws12 that the gap 11 has an equal width at all points. Near the upper endof the tube 8 a reservoir 13 is placed, which surrounds the jacket 8.Through inlets 14 the coagulation liquid is supplied via an overflowcylinder 15 and holes 16 in the jacket 8. The excess liquid is drainedofi from the cylinder 15 through an overflow pipe 17.

Figure 2 shows an embodiment that is essentially the same as that ofFigure 1. Here again the viscose supply tube 1 is cylindrical over itsentire length but at its lower end the cylindrical spinneret holder 2 isscrewed on to it. Between the lower end of the tube 1 and the spinneretholder 2 is the packing 18. The supply pipe 14 for the coagulationliquid is directly connected with the jacket 8. The cone 10 is screwedonto the tube 8, and ends in a ring 19, which surrounds the spinneretholder 2, but does not reach to its lower end. The ring 19 is so groundat its lower end that it has a sharp edge at the inner side thereof.

For sealing the connection between the jacket 8 and the cone 10 a washer20 is provided, while centering 'members 21 are provided therein forcorrectly centering 24 serves for sealing the tube 1 passing through thereduced upper end 22 of the jacket 8.

As indicated above, a great increase of the working speed in thespinning room may be acquired with the method and apparatus according tothe present invention.

It has been discovered, moreover, that the viscose rayon threadsobtained are of excellent quality, and that in combination with thestretching of the freshly set thread remarkable improvements, of anature to be described below, are obtained.

The measures heretofore described in connection with the two embodimentsof the invention serve the purpose of satisfactorily guiding thecoagulation liquid to the spinneret in'a uniform manner. A high pressureon the coagulation liquid, or a high squirting velocity, is avoided. Theamount of coagulation liquid can be readily adjusted and it is onlynecessary that such an amount be supplied that all the viscose filamentsare enveloped and are adhesively combined into one whole. Thecoagulation liquid envelopes the whole in the manner of a sheath, and acomplete coagulation and at least a partial decomposition are therebybrought about.

The decomposing action of the thus-supplied coagulation liquid need notbe sufficient for the complete decomposition of the viscose. In asubsequent part of the spinning path a second bath may be employed todecompose the viscose further, or the thread may be led through a hotstretching bath whereby the partially decomposed viscose is completelyconverted into cellulose hydrate by means of heat or by the combinedaction of heat and acid.

According to the present invention, the freshly set thread takes with itso much coagulation liquid as is supplied. No spinning bath proper,relatively stationary, through which the thread must go for whateverdefinite immersion length, is present.

In addition to the uniformly divided and concentric supply of thecoagulation liquid to the spinneret, there is the definite advantagethat the guiding path of the liquid is not interrupted. The adhesive andguiding forces, which 'act between the spinneret holder and thecoagulation liquid, may thus have their full and undisturbed effects onthe viscose spinning operation.

One of the outstanding advantages obtained with the method and deviceaccording to the present invention is more prevalent when the thread,which is drawn off at high speed by means of a driven, primarydrawing-01f member, is stretched afterwards, or, what is almost thesame, when the thread is stretched over a braking member at highdrawing-01f speed. It has been discovered that the productstrengthXelongation only slowly decreases with increasing primarydrawing-otf speed.

It must be assumed that the new thread (in contrast with the present daythreads) spun at a very high drawing-otf speed, has, during the firstpart of the spinning path, and at any rate before the after-stretching,a constitution unaffected by premature overstretching, which, as isgenerally known, is not to be expected when employing spinning bathsproperly so called, however small their lengths, e. g. a few cm.

According to the method of the present invention, any viscose hithertoconsidered workable may be spun. The requirements in respect of maturityor temperature or other viscose properties are no different from thosemet with in the hitherto known methods for the manufacture of viscoserayon. All coagulation baths are suitable, such as the conventionalMuller baths as well as those with special compositions adapted tospecial purposes. In general, high-acid spinning baths allow of a higherprimary drawing-01f speed than low-acid baths which less rapidlycoagulate and decompose the cellulose Xanthate. It has been found,however, that according to the method of the present invention low-acidbaths, too, may be advantageously employed since they equally allowspinning at a rather considerable increase of primary drawing-off speed,in contrast with the known methods. Normal Muller baths with high zincsulphate content permit spinning at equally high speed, though it is notpossible to attain the highest primary drawing-off speeds. With normalMuller baths containing little or no zinc sulphate, spinning accordingto the method of this invention may be done at drawing-off speeds of 250m./min. and higher.

\ In spinning according to the present invention there is no problemconcerning the length of immersion in a coagulation bath bounded bywalls, nor about upsetting or constriction of the liquid or particularconstriction of the bundle of filaments. The measures described hereinare also taken to prevent a harmful formation of turbulence inthecoagulation liquid carried along by the thread, or to avoid unduefrictional forces on the still-very-sensitive 'freshly formed thread.

The amount of coagulation liquid is adjusted to conform to the spinningconditions, according to the coagulating and decomposing properties ofthe coagulation liquid itselflthe properties of the viscose, the titreof the threadto be spun, the primary drawing-0E speed, etc.

Experiments have shown that one cardinal cause of the highly beneficialeffects of the method according to the present invention is that at theface of the spinneret 'there is never more coagulation liquid than iscontinuously carried away by the thread. No accumulation of coagulationliquid can take place so that turbulence forbreakage are avoided.

The artificial threads obtained according to the method of the presentinvention are, inspite of the abnormally high primary drawing-off speed,of excellent quality. Viscose rayon threads of all common types may bespun, e. g. 15- -20 denier, -120 denier, and finally 1000-1500 denier,which are especially useful in the manufacture of automobile tirefabrics.

The, ease of dismantling the spinning device according to this inventionhas given complete satisfaction in practice, both for inspection of theviscosesupply pipe and of the supply device for the coagulation liquid,for changing the spinneret, and for centering the spinneret holder.

In the devices described according to Figures 1 and 2, the viscosesupply line 1 can easily be displaced axially in the jacket 8 and, as aconsequence, the distance between the spinneret 3 and the outlet for thecoagulation liquid can easily be adjusted at will. The connectionbetween the line 1 and the vessel'or jacket 8 is not entirely stiif orrigid, and yet it is still possible to lead the coagulation liquid underpressure into the coagulation liquid vessel.

Spinning-in with the devices according to Figures 1 and 2 may be carriedout as follows:

The outlet of the empty coagulation liquid vessel is closed, and thevessel filled with water. Then the viscose supply cylinder is opened sothat the viscose passes through the spinning holes and the water in thevessel is gradually replaced by the coagulation liquid proper.

In four experiments described below by way of example, a deviceaccording to Figure 2 was used, the procedure being that schematicallyindicated in Figure 3. There, after emerging from the spinneret 3, thethread was led vertically downwardly and around a primary draw-01f godet25 at a distance of 60 cm. below the spinneret. Then the thread was ledseveral times around a second godet 26 driven at a slightly highercircumferential speed than godet 25. In its further path of travel thethread was laid in several turns around a stretching roller 27 and wasthen led into the spinning pot 28 disposed below the roller 27.

The godet 26 imparted a small stretch of about 3% to the thread. Thestretching roller 2'7 stretched the thread with respect to the primarydraw-oft of roller 25 about 30%, so that the final titre of the threadwas 110 denier.

The viscose as spun had a cellulose content of 7.3%, an alkali contentof 6.8% and a maturity of 11 Hottenroth. A spinneret was used having 40holes, each of 70 microns. The coagulation liquid contained per litre110 g. of sulphuric acid, 175 g. of sodium sulphate, 40 g. of magnesiumsulphate, and 8 g. of Zinc sulphate. The liquid temperature was 70 C.The amount of coagulation liquid taken along With the thread from thespinneret was adjusted to about 225 cm. /min.

The following table shows the spinning speeds used and the resultsobtained:

Primary Spinning drawingspeed Exp. on speed Strength,

Elongation, g./100 denier percent in mJmin. m./min. dry wet dry wetWhile specific details of preferred embodiments have been set forthabove, it will be apparent that many changes and modifications may bemade therein without departing from the spirit of the invention. it willtherefore be understood that what has-been described herein is intendedto be illustrative only, and is not intended to limit the scope of theinvention.

What is claimed is:

1. Apparatus for the jet spinning of artificial threads from viscosecomprising an elongated cylinder through which viscose is supplied, atubular spinneret holder secured to one end of said cylinder, the outersurface of said spinneret holder forming a smooth extension of the outersurface of said cylinder, a flat spinneret having a plurality of holesmounted in the end of said spinneret holder, an elongated jacketsurrounding said cylinder in spaced relationship and extending over aportion thereof, means at one end of said jacket for closing the spacebetween the cylinder and jacket, means secured to and defining the otherend of said jacket for restricting the space between the jacket andcylinder and for forming an annular gap through which coagulating liquiduniformly flows at a point remote from the face of the spinneret,means-adjacent the closed end of said jacket for supplying coagulatingliquid to the space between the jacket and cylinder and adjustable meansfor spacing the jacket concentrically with respect to the cylinder,whereby the coagulating liquid envelopes the threads formed duringspinning in the manner of a sheath.

2. An apparatus for jet spinning as set forth in claim 1 wherein thespinneret holder is cylindrical in shape and is provided with roundededges in order to enhance the streamline flow of coagulating liquid.

3. An apparatus for jet spinning as set forth in claim 1 wherein themeans for supplying coagulating liquid comprises a reservoir whichsurrounds said jaacket.

References Cited in the file of this patent UNITED STATES PATENTS2,510,135 Pedlow et a1. June 6, 1950 FOREIGN PATENTS 168,830 GermanyJune 21, 1904 394,049 Great Britain June 22, 1933

